This invention relates to novel t-aliphatic .alpha.-(sulfo) azo compounds (I), and to their use as polymerization initiators for vinyl monomers and as curing agents for polyester resin compositions.
To the best of applicants' knowledge, no .alpha.-(sulfo) azo compounds of structure I have been previously reported.
U.S. Pat. No. 3,282,912 and Canadian Pat. No. 750,380 report .alpha.-sulfoazo compounds of structures II and III, respectively: ##EQU2## Compounds II are symmetrical azo compounds and thus are in a completely different category from the subject unsymmetrical t-aliphatic azo compounds (I). For example, symmetrical azo compounds have much lower decomposition temperatures (i.e., are much less stable) than the corresponding unsymmetrical t-aliphatic I compounds derived from the same ketone. When R.sub.1 is methyl, R.sub.2 is isobutyl and R.sub.3 is phenyl, compound II is a solid having a 10 hour half-life at about 82.degree.C., while compound I of this invention is a liquid having a 10 hour half-life at about 118.degree.C. making I more useful for high-temperature applications. While compounds III are unsymmetrical, they include cyano groups (rather than R" as in compound I) which increase toxicity problems and decrease hydrocarbon solubility. Further, it is not evident from Canadian Pat. No. 750,830 that any compounds of structure III were ever made and no preparatory examples are given. Statements in the patent further indicate that compounds III would be less stable than the instant compounds I.